When a blood flow velocity, etc., are measured, as described in Japanese Patent No. 3403917, for example, an ultrasonograph displays a color flow mapping image showing the state of a blood flow such as the movement of a blood flow, the direction of a blood flow, etc., superimposed on an ultrasonic image (B image) of a diagnostic portion. This color flow mapping image is generated in a Doppler color box (interest area) set on the B image. Then, a Doppler sample gate (display mark) superimposed on a blood vessel in the color flow mapping image in the Doppler color box is displayed and a blood flow velocity, etc., are measured based on a reflection echo signal of an area sandwiched in a Doppler sample gate. These Doppler sample gate and Doppler color box are generally set such that the display position on a screen is moved by a pointing device such as a track ball, etc.
Now, ultrasonic images and color flow mapping images obtained from the ultrasonograph are generally displayed in the shape of a sector (for example, the central angle of a sectoral image is 30 to 120°). In a tack ball, for example, it is made that the amount of movement in the vertical direction of a display image corresponds to the depth position of an ultrasonic beam line and the amount of movement in the horizontal direction corresponds to the scanning direction of the ultrasonic beam line.
However, along the development of ultrasonic diagnostic technology, there are cases where images of a wide visual field or of a sectoral portion of a wide central angle (for example 180° or more) are obtained. For example, there is a case where an ultrasonic probe in which ultrasonic transducers are provided around a cylinder and which can perform an omni-directional scanning (360°) is inserted into a coelom such as an esophagus, an ultrasonic beam is radiated from the ultrasonic probe in the center, and a circular ultrasonic image seen from the inside of the coelom is obtained.
While such a sectoral or circular image of a wide visual field is seen, when the Doppler sample gate and the interest area are moved by a conventional operating method, since the operating direction of the track ball is greatly different from the target direction of a Doppler sample gate on the screen, there is a problem in that the feeling of strangeness is caused in the operation of the track ball and the operability is lowered.
Such a problem in the operability for setting the position of a display mark is not limited to the Doppler sampling gate, and there is the same problem in the operation of movement of an interest area such as a color box in the color flow mapping, etc.
It is an object of the present invention to improve the operability in movement of a display body designating a measurement portion, etc.